Automotive seats usually comprise a seat bottom that is affixed to a seat frame. The seat frame is mounted to the floor of the vehicle and is usually of a rail-type design to allow the forward and rearward adjustment of the seat bottom. The seat back is attached to the seat bottom by a seat back support. If the seat is a reclining type seat where the seat back is rotationally movable with respect to the seat bottom, a locking and release mechanism must be provided. The seat reclining mechanism usually comprises a base that is affixed to the structure of the seat bottom. The seat back support is pivotally mounted to such base as it is desirable to have the seat back move forward and rearward with the seat bottom. The locking and release mechanism by which the seat back is held in a fixed angular position relative to the seat bottom has several known forms. One form is a ratchet mechanism wherein a notched wheel is fixed to either the seat back or seat bottom and a pawl is attached to the other. Upon the pawl disengaging the notched wheel, the seat back is released and is free to rotate at its pivot with respect to the seat bottom. Other types of engaging or intermeshing gear type mechanisms will provide a locking and a releasing operation between the seat bottom and seat back.
As a customer comfort and convenience feature, many motor vehicles are now equipped with automated seat reclining mechanisms which allow the seat occupants to recline the seat back to a desired position. For some motor vehicles, and particularly those for the luxury market, the recliner mechanism is electrically powered.
Although equally applicable to manual seat back adjusters, the present invention is particularly related to an improved power type reclining mechanism.
The use of inertia latches in motor vehicle seat back recliners is known, particularly in two-door type vehicles, to facilitate rear seat entry and egress. Such latches provide for free displacement of the front seat back from its set position to a forward position when the vehicle is stationary but, through use of an inertia member, cause the seat back to be momentarily locked in its set position during periods of high de-acceleration such as during emergency braking of the vehicle.
Such prior art inertia latch devices have been unsatisfactory in several respects. First, because they are typically in the release condition during normal operation, a malfunction may result in non-engagement during a vehicle impact without providing advance warning to the operator. Secondly, even with proper operation, prior art inertia devices require that the inertia member be rapidly displaced from the release position to the engaged position during incipient movement of the seat back under high de-acceleration conditions. This necessary displacement of the inertia member necessarily permits a given degree of lost motion movement of the seat back prior to engagement. Under certain conditions, it has been found that a front seat vehicle occupant's shoulder harness becomes taunt prior to engagement of the seat back inertia latch. This is highly undesirable inasmuch as an unrestrained rear seat object or passenger can impact the rear surface of the front seat back prior to engagement of the inertia latch, causing unacceptably high impact loading on the operator's chest region via his shoulder belt or harness.